Refrigerating apparatus



Feb. 4, 1941. a Y 2,230,842

REFR IGERAT IN G APPARATUS Filed Sept. 8, 1939 2 Sheets-Sheet 1 zmmx m.77?

FY Way/M ATTa/PNEK Feb. 4, 1941. E. M. MAY

REFRIGERATINGLAPPARATUS 2 Sheets-Sheet 2 Filed Sept. 8, 1939 ATrORNEKPatented Feb. 4, 1941 UNITED- STAT-ES PATENT orrica 3 Claims.

The invention relates to refrigerating apparatus and particularly tosuch apparatus of the automatic intermittently cycling type.

In automatic refrigerating apparatus now in 5' common use, such forexample as that of the common household refrigerator, the systemcomprises an evaporator in which liquid refrigerant is evaporated toproduce the desired cooling effect and refrigerant condensing meanswhich withm draws the refrigerant vapor from the evaporator and restoresit to the liquid state for reuse in the evaporator, variations of thetemperature or pressure within the evaporator, or other part of the lowside of the system being utilized to control 15 the operation of thecondensing means and usually to start and stop it. Now, the heat, loadto which such refrigerating apparatus is subjected in service may varywidely, and it has been found that under a light heat load the operationof the 20. evaporator of such a system is sluggish, it being necessaryto reduce the pressure in the evaporator to a relatively low value inorder to initiate ebullition; and the production of this necessary lowpressure lowers the over-all eiilciency of the apparatus.

The general object of the present invention is to provide refrigeratingapparatus of the character in question in which the evaporator is moreresponsive to the suction effect of the condensing iii-means under lightheat loads, with resultant im-' provement in the emciency of operation.

More specifically, it is an object ofthe invention to providerefrigerating apparatus of the character in question having means forauto- 15: matically agitating the liquid refrigerant in the evaporatorwhen the refrigerant condensing means is .in operation and especiallyduring the p first part of such operation.

,Another specific object of the invention is to L efiect the agitationof the liquid refrigerant referred to above by introducing refrigerantvapor into the liquid refrigerant in the evaporator.

And a still further object of the invention is to provide refrigeratingapparatus having simple,-

l inexpensive and effective means for the introduction of refrigerantvapor into the liquid refrigerant space of the evaporator to stimulateebu1lition.

With the above objects and others more or less 50 incidental orancillary thereto in view the invention consists in certain combinationsof parts and features of construction which will appear in the followingdescription of certain specific embodiments of the invention shown inthe accompanying drawings.

.In the'drawlngs,

Fig. 1 is a view partly in'sectional elevation and partly diagrammaticof a refrigerating system embodying the invention.

Fig. 2 is an enlargedyie'w partly in section and 5 partly in elevationof fragmentary parts'of the apparatus shown in Fig. 1.

Fig. 3 is a view partly in elevation and partlydiagrammatic of arefrigeration system similar to that shown in Fig. 1 but with theinvention applied to a different type of refrigerant evaporator.

Fig. 4 is an enlarged section on the line 44 of Fi 3.

Fig. 5 is a view partly in sectional elevation and partly diagrammaticof a refrigeration system embodying the invention as applied to anevaporator of the flooded type with low side float valve.

Fig. 6 is a view partly in sectional elevation and partly diagrammaticof a refrigeration system showing the invention as applied to another.form of flooded evaporator with high side float valve.

Referring in detail to the construction shown in Figs. 1 and 2,1designates a refrigerant evaporator in the form of an upright continuouscoil designed to cool a refrigerator or container 2 of the top-openingbox type, only the side and bottom walls of the refrigerator beingindicated. The inlet arm la of the evaporator coil I is connected to aT- coupling 3 to which in turn is connected a thermostatic expansionvalve 4 designed to be automatically operated by pressure generated in athermostatic bulb 5 which has heat-transmitting engagement with theoutlet end of the evaporator coil I and which is connected with thevalved by means of a small bore tube 8. The internal construction of thevalve d is not shown as any known thermostatic expansion valve can beused.

' The numeral 1 designates as an entirety a motor-driven refrigerantcompressor having its suction inlet connected by a pipe 8 with thedischarge branch lb of the evaporator coil I. A condenser 9 is connectedby a pipe ID to the discharge of compressor I and the condenser in turnis connected to a liquid refrigerant. receiver I] by pipe l2. ReceiverII is connected by a liquid refrigerant line l3 with the inlet of theexpan- 5 sion valve 4, thus completing the closed circuit of the system.The motor of the compressor set is connected by suitable conductors l4and man'- ual switch IS with a; current source-l8 and apressure-actuated switch I! is provided to automatically control thecompressor motor, said switch being actuated by fluid pressure generatedin a thermostatic bulb I8 having heat-conducting contact withthe outletportion of the evaporator and being connected by small bore tube I9 withthe pressure chamber of the switch I1.

All of the above described parts of the apparatus are of well known typeand construction. In the operation of such systems the absorption ofheat by the evaporator coil I raises the temperature of thermostaticbulb I8 which results in the closing of switch I1 and the starting ofthe motordriven compressor I. The suction of the compressor in the firstpart of the period of its operation reduces the pressure in theevaporator coil I while the valve bulb 5 remains relatively warm. Thispermits expansion valve 4 to open and admit liquid refrigerant throughthe T connection 3 into inlet section Ia of the evaporator. Meanwhileliquid refrigerant in the bottom turn or turns of the evaporator coil Itendsto lie quiescent and in prior apparatus of this kind, as wasindicatedat the outset, it has been necessary to carry the suctionpressure of the evaporator to a relatively low value before activeebullition of the liquid refrigerant in the lower part of the coil wouldbegin, this being especially true where the heat load on the evaporatorwas relatively low. Furthermore,

into the body of liquid refrigerant. This I ac- I complish in theapparatus illustrated by means now to be described.

In the apparatus shown in Fig. 1, the upper branch or passage of the Tcoupling 3 is connected by means of a small bore tube 20 with a liquidrefrigerant container 2I in the form of a tubular bulb which is arrangedin heat transmitting connection with the upper, outletturn of the coilIr" Asis, shown in Fig. 2, the end of the tube 20- projects well intothe chamber of the container 2|.

In the operation of the apparatus the tube 20 and container 2I,connected as described to coupling' 3, function in the following manner.Toward the end of a running period of the apparatus .the temperaturethroughout the evaporator coil I is lowered, the outlet portion of the.0011 being slightly colder than the inlet part thereof. Under theseconditions condensation of refrigerant yapor occurs in bulb 2| and someof the liquid refrigerant admitted to the T coupling by the expansionvalve is drawn through tube 20 into bulb 2| where at least some of it istrapped. When the temperature of the evaporator has been reduced to apredetermined point, the condensing means is shut ofl and the usual offor idle period follows. During theidle perioda converse condition of theevaporator develops; that is, the outlet part of the evaporator becomeswarmer than its inlet part. This causw refrigerant trapped in the bulb.2I to evaporate with the resuit that the gaseous refrigerant is forcedback through tube 20 and T coupling 3 into and through the evaporator.This action is especially marked when the comprm first starts at thebeginning of the operating period due to the liquid refrigerant at thebeginning of the working period of the cycleof operation increases theoverall efliciency of the apparatus because the suction pressure of thesystem does not have to be carried as low, to attain a given evaporatortemperature, as when such agitation is not supplied. This advantage, ashas been indicated, is especially marked when the heat load on theevaporator is relatively low or moderate.

The present invention is not limited to apparatus having evaporators ofthe particular type illustratedin Fig. 1. As indicative of some of theother possible applications of the invention I have shown suchapplications in other figures of the drawing to several forms or typesof evaporator.

In Fig. 3 the pants Ia, 8a, 9a, Illa, Ila, I211, I311, Ila, I 5a, I611,I10, I811. and I9a are respectively substantially identical'with thecorresponding parts'l,8, 9, I0, II,I2, I3, I4, I5, I6, I1, I8 and I9 ofthe system showni, in Fig. 1. But in lieu of the vertical coil type ofevaporator shown in Fig. 1 the apparatus in Fig. 3 has an evaporatorcomprising a. horizontally disposed expansion coil 22 and a metal shell23 with the exterior of which coil 22 has heat transmitting connection.The shell 23 is .of the type provided with ice or food trays such as areshown at 24. The coil 22 has its inlet arm 22a connected to a T coupling25, which in turn is connected to an automatic expansion yalve 26 whichmay be of the known types of construction suitable for use in connectionwith such evaporators. The inlet of the valve 26 is connected with theliquid line I3a of the system, and the outlet 22b of the evaporator coilis connected with the suction line 8a of the system. Thermal bulb I8aoperatively connected. with control switch I'Ia. is arranged in heattransmitting connection with the evaporator shell 23 at or near theoutlet end of the evaporator.

In this apparatus the T coupling 25, as best shown in Fig. 4, isconnected by tube 21 to an ebullator bulb 28 which is in heattransmitting engagement with the evaporator shell 23 near the outlet endof the evaporator.

Except for the automatic action of the expansion valve 26 the system ofFig. 3 is substantially the same in operation as that of Fig. 1. Theoperation of the ebullator 28 in Fig. 3 also is similar to the operation'of the ebullator in Fig. 1

and it is believed it will be clear without further,

description. I

In Fig. 5 of the drawings, the invention is shown lower ends of tubes29bare connected. The

evaporator is fitted with a float-controlled inlet 2,280,842 valve 30 towhich the liquid refrigerant supply line l3b is connected, and with asuction outlet tube 3| to which the suction line to is connected.

In the operation of a system having a flooded evaporator such as isshown, the float valve 33 admits liquid refrigerant to the evaporator asrefrigerant is evaporated therein so as to maintain the refrigerant at asubstantially constant level as indicated in Fig. 5, theopen upper endof the suction tube 3| being thus disposed in the vapor space of theevaporator. In an evaporator of the flooded type the top wall thereof,during the ofi or idle period, is the warmest part of the evaporatorbecause it is not in direct contact' with liquid refrigerant.Accordingly the top wall of the header 29a corresponds to the outletportion of the evaporator coil I in Fig. 1 and the switch bulb lBb isarranged in contact with the top wall of the header.

The ebullator in Fig. is substantially the same as that in theabovedescribed systems and comprises a smallbore tube 32 which is'connected with the lower header 230 as shown, and an ebullator bulb 33which is similar in construction to the bulb 2i shown in Fig. 2, havingthe end of tube 32 projecting into the chamber of the bulb so as to trapliquid refrigerant therein as explained in connection with the firstdescribed system. i

In the operation of the apparatus in Fig. 5 all parts of the evaporatorare lowered in temperature during the working period of the cycle andthis results in condensation in the ebullator bulb 33, causing liquidrefrigerant to be drawn from the lower header 29 into the ebullator bulb33. Later, during the idle period of the compressor, the temperature ofthe evaporator rises, evaporation occurs in the ebullator andrefrigerant vapor is forced into the lower header 230 so as to risethrough the liquid refrigerant and agitate it and stimulate ebullitionas explained in connection with the first described system.

In Fig. 6 of the drawings, the invention is shown applied to a floodedevaporator with high side float valve. Here the parts lo, 30, 30, lo,lie, lzc, Me, Me, I50, lGc, I10, I80 and I90 are substantially the sameas the corresponding parts I, 3, 9, I3, ll, l2, l3, I3, l5, it, Hi, Itand I3 of the system shown in Fig. 1.

The evaporator as is of the hollow shell type and comprises outer andinner walls 33a and 33b in the form of metal sheets bent intoapproximately U form and spaced apart to form refrigerant chamber 340.The two upright branches of the chamber so formed are connected by atleast one transverse tube 33d which is fittedwith a suction outlet tube34c to which the suction line 80 is connected. A' high side float valve35, which may be of any suitable known construction, has its inletconnected with the liquid refrigerant line I30, and its outletconnectedby tube 35 to the inlet 31, in the bottom of the'evaporator 33.

orator such as the 1 evaporator 34, the high, side float valve admitsliquid refrigerant to the evaporator as "refrigerant is withdrawn fromthe evaporator, condensed and-returned to the float" valve chamber; andthus maintains the refrigerant in the evaporator at a suitable level asindicated in Fig. 6. As in the case of the evaporator 29 of Fig. 5, theevaporator 34 has its wall parts above the liquid level warmer thanother parts of the evaporator during the idle period of the apparatus,and the switch bulb I80 is arranged in heat conducting contact with thetop wall of the evaporator 34 as shown.

The ebullator for the evaporator 34 comprises small bore tube 38 whichis connected at one end with an ebullator bulb 39, and at its other endis connected to passage lilformed in the same fitting as the refrigerantinlet 31, thus operatively connecting the ebullator bulb with the bottompart of the evaporator chamber 840. The ebullator bulb 39 is secured inheat transmitting connection with the top wall of the evaporator and isof the same construction as the bulb 2| shown in Fig. 2, having the endof the tube 33 projecting into the bulb chamber.

In the operation of the last described apparatus all parts of theevaporator are lowered in temperature duringthe working period of thecycle; This results in condensation of refrigerant in the ebullator bulb39 which in turn causes liquid refrigerant to be drawn from the bottomof the evaporator into the ebullator bulb. Later, during the idle periodof the apparatus, the temperature of the evaporator rises andevaporation of refrigerant occurs in the ebullator so that refrigerantvapor is forced therefrom into the bottom of the evaporator causingagitation of the liquid refrigerant therein and stimulating ebullitionas explained in connection with the systems already described.

It will be understood that means of various kinds can be employed toeffect automatically a positive agitation of the liquid refrigerant inthe evaporator at appropriate times in the operating cycle, but I-prefer to accomplish this agitation by the introduction of refrigerantvapor into the liquid refrigerant and, furthermore, I especially preferto accomplish this by means of a refrigerant bulb or trap operativelyassociated with the evaporator in ways such as have been shown in thedrawings and described above, because of the extreme simplicity of saidconstruction and its reliability andeffectiveness in operation.

What I claim is:

1.' In a refrigerating system, the combination with a refrigerantevaporator having an inlet for refrigerant liquid and an outlet forrefrigerant vapor leading from the vapor space of the evaporator;refrigerant condensing means having its refrigerant vapor inletconnected with the said outlet of the evaporator and its refrigerantoutlet connected with the said inlet of the evaporator; means forcontrolling. admission of liquid refrigerant into the evaporator; andcontrol means for the refrigerant condensing means causing the latter tooperate intermittently to withdraw refrigerant from the said vapor spaceof the evaporator; of means for introducing refrigerant vapor into thelower part of the evaporator at a time when refrigerant is beingwithdrawn fromthe latter by the condensing means, the said means forintroducing vapor comprising a refrigerant container having goodheat-conducting connection with that part of the evap orator wallenclosing the said vapor space of the evaporator; and conduit meansleading from the interior of the said container into a liquid-containingpart of the evaporator, whereby liquid refrigerant is drawn into thecontainer in the in which the evaporator is in the form .of a con- 7tinuous coil of pipe and an expansion valve serves to control admissionof liquid refrigerant into it.

3. A refrigerating system as claimed in, claim 1 in which the evaporatoris of the flooded type and a float actuated valve serves to control ad-5 mission of liquid refrigerant into it.

EDWARD M. MAY.

